Electrical musical instrument



Feb. 21, 1950 EL. KENT 2,498,337

ELECTRICAL MUSICAL INSTRUMENT Filed April 20, 1945 2 Shets-Sheet l POWER 4MPL/ F If R Hu g TERM.

GEN

i wi /3% Patented Feb. 21, 1950 UNITED ELECTRICAL MUSICAL INSTRUMENT Earle L. Kent, Elkhart, Ind., assignor to C. G.

Conn, Ltd., Elkhart, Ind., a corporation of Indiana Application April 20, 1945, Serial No. 589,345

3 Claims.

This invention relates to electrical musical instruments and more particularly to electrical 1nstruments of the keyboard type for producing effects similar to a pipe organ.

One of the objects of the invention is to provide an instrument having substantial flexibility of control to produce organ like or instrument tones, as desired.

Another object is to provide an instrument in which a plurality of different tones may be produced simultaneously in additive fashion.

Still another object is to provide an instrument in which the tonal quality or harmonic content of the tones can be controlled, as desired, to produce different tonal effects.

A further object is to provide an instrument in which a wide variety of tonal effects can be obtained with a minimum number of parts and with a relatively simple keying arrangement.

A still further object is to provide an instrument in which the desired tonal effects are obtained by controlling the relative intensity of the fundamental and harmonic vibrations. In a preferred construction, undesirable frequencies are filtered or attenuated to the extent necessary "for the production of the desired tonal qualities.

A still further object is to provide an instrument in which the desired tonal effects are produced by mixing oscillations of different harmonic contents.

The above and other objects and advantages of the invention will be more readily apparent from the following description when read in connection with the accompanying drawing in which Figure 1 is a block diagram of a part of an instrument embodying the invention;

Figure 2 is a circuit diagram; and

Figure 3 is a circuit diagram of one of the stop mixers.

The instrument of the present invention comprises essentially a plurality of vibration generators, one for each note, and each of which produces vibrations of two different tone qualities or harmonic contents. Keying and coupling means are provided to control the operation of the generators and the vibrations are supplied to a translating device such as a loud-speaker through selected paths in which means are included to control the relative intensities of the several frequencies present. By this means, selected tone qualities can be produced at the translating device similar to the several standard organ stops or involving unique tonaljeffects.

The block diagram of Figure 1 indicates a plurality of oscillators l0 tuned to produce osci1lations or vibrations corresponding to the frequencies of the several notes of a musical scale. Any desired type of vibration generators or oscillators may be employed such, for example, as the oscillators disclosed in the patent to McKellip et al. No. 2,340,002. In oscillators of this type, vibrations approaching a pure sine wave to produce a flute tone are derived from the tank circuit while oscillations rich in harmonics to produce a string tone are derived from the cathode circuit. As shown, the several resistors across the tank circuit transformers are connected in series by a wire II in the manner described in the McKellip patent and the several cathode circuits are connected in parallel to a wire l2 in the manner described in the McKellip patent.

The oscillators are controlled through keying and coupling switches I3 and I4 so that operation of the respective oscillators will be initiated. when the switches are closed. The keying and coupling switches may control the oscillators as described in the McKellip patent, but as shown they connect the control grids of the oscillator tubes, which may be triodes to ground through a line [5. A switch 16 is provided in line l5 to connect the keying and coupling switches directly to ground through a resistor I! or through a low frequency tremolo generator l8. When the generator I8 is connected in the circuit, it causes a low frequency variation in the oscillator outputs to produce a tremolo or vibrato effect.

The wires II and I2 are connected to an input mixer 19 in which the several flute tones are combined and the several string tones are separately combined. The flute tone oscillations are transmitted from the input mixer through a line 2! and the string tone oscillations are similarly transmitted through a line 22. The input mixer may be made adjustable, as will appear more fully hereinafter, to vary the relative over-all strengths of the flute and string tones, as desired.

A plurality of stop mixers 23, 24 and 25 are connected in parallel between the lines 2! and 22 and a line 26 leading to an output mixer 21. It will be understood that while only three stop mixers are illustrated, any desired number could be provided to produce the desired variations in tonal efiects. As shown, the stop mixer 23 is connected to both lines 2| and 22 and is provided with manual adjustment 28 by which the relative intensities of the fluteand strong tones ,canbe varied to vary the harmonic content of the mixer output. By this means various tonal effects can be obtained according to the desires of the operator.

The succeeding stop mixers 24 and 25 and such other stop mixers as may be provided are preferably "fixed devices which are so constructed as to produce'tone qualities corresponding to the several standard organ stops. As shown, the mixer 24 is connected only to the flute output line 2| to produce a flute stop while the mixer 25 is connected to both lines 2! and 22 to produce a tone having a desired harmonic content similar to a selected one ofthe standard organ stops.

The output mixer 2'! mixes the several tones supplied through the stop mixers and delivers them to a swell control resistor 33. Anadjustable wiper 29 engages the resistor 30 and is connected through a power amplifier 31 to a translating device shown as a loud-speaker 32.

Inoperatingthe organ, theoperator may selectively mane effective any one or more of the several stop mixers and the tonal quality of the organ will depend uponthe stop mixers selected. Since the stop mixers areall connected in parallel their effect will be additive so that operation of theorgan with several of the stops effective will be substantially identical with corresponding op- .eration'oi a conventional pipe organ. When using the manual stop mixer 23, various standard, as 'well as unique tonal effects, can be produced by adjusting the relative intensities of the "flute and string type vibrations to control the harmonic content of the tone.

Figure 2,.il1ustrates incircuit diagram, the circuit :from the input mixer to the translating device. .As 'shown,:the input mixer is in two sections, the upper section being the flute tone section and the lower being the string tone section. The vibrations corresponding to the flute tone are suppliedrat a terminal 33 through a variable resistor 34 to the grid of a tube 35 shown as a triode. The cathode of the tube 35 is connected to Iground'as shownand to the cathode of a second tube 36also illustrated as a triode. The plate of the'tube 35 is connectedithroug'h a:load'resistor '31 to a terminal 38 leading to a suitable source of plate supply voltage. A blocking condenser 39 connects the plate circuit to the line 2i.

The string section includes a terminal M to which string type vibrations are supplied and which supplies the primary of a transformer 42. The secondary. of the transformer is connected to the grid of a tube 43 through a variable relsistor 4s. The plate of the tube 33 is connected to the terminal 38 through a .load resistor 45 and through a blocking condenser '46 to the line 22.

The manual stopmixer 23 comprises the tube '36and a similar tube 41 whose plate circuits are interconnected and are supplied with plate voltage through a load resistor 48. Both plates are connected through a blocking condenser 49 and a resistor 5i to'the line 26 leading to the output mix'er.

The tube 36 is supplied from the flute mixer tube 135 through a fixed resistor 53 and a variable resistor 52 which is connected to its grid. The tube '41 is similarly supplied from the plate circuit 43 through a fixed resistor 50' and a variable resistor '53. The resistors 52 and "53 are adapted to be adjusted as desired to determine the intensities of the flute and string tones respectively. Higher frequencies in the" outputs "may be variably attenuated to-produce a tone control by variableresistors 52" and 53'- connected .in serieswith condensers across the grid circuits of the tubes 36 and 4'! respectively. These resistors may be adjusted simultaneously through a connecting linkage 54 controlled by a manual control button, such as the button 28 of Figure 1. By means of these adjustments, the relative intensities and the harmonic contents of the outputs of tubes 36 andfll can be varied. Since the flute tone is a substantially pure sine wave while the string tone includes a considerable number of harmonics, it will be seen that by this adjustment the harmonic content of the output supplied to the line 26 can be controlled throughout a wide range. The manual stop mixer is controlled by a stop switch 55 connecting the combined plate circuit outputs to the cathode circuits to short circuit the tubes so that when the switch is closed the manual stop mixer will not be in operation.

The stop mixer 24, as illustrated in Figure 2, comprises-atub'e 53shown as a triode tube having its plate connected through a resistor 51 to a wire 58 leading to a suitable source of platesupply voltage. The plate is additionally connected through a blocking condenser 59 and resistor 6| to the output line 28 leading to the output mixer. The control grid of the tube 56 is supplied irom the line 2| through a resistor 62 and is connected to the cathode of the tube through a resistor 33. When the stop mixer. is inoperation the tube 56 will be controlled by flute type oscillations supplied through the line M to supply similar oscillations to the output line 26. The operation of the mixer is controlled by a switch 64 short circuiting the-grid cathode circuit of the tube so that when the switch is closed, the tube'will not transmit.

The stop mixer'25 includes a tube 65 shown as a triode whose plate is connected to the wire 58 through a resistor 63 and to the output line 26 through a blocking condenser 61 and resistor 68. The control grid of the tube is supplied from both lines 2! and 22 through resistors 69 and H respectively which have a common connection to the grid. The grid cathode circuit is formed through a resistor 12 and operationof the tube is controlled by a switch 73 short circuiting the grid cathode circuit of the tube.

To bring any one of the stop mixers, such as 2 3 and 25 into operation, the respective control switches, such as 64 and 13, are opened. At this time, the tube forming a part of th mixer will transmit to supply oscillations to the output line 26. By controlling the relative values of the several circuit elements and particularly the resistors, such as 69 and 'ii, the relative intensities of the flute and string signals can be controlled to produce the desired harmonic content in the mixer output. Thus the mixers may be designed to produce harmonic contents respectively similar to those of the several standard organ stops or to produce such other unique effects as may be desired.

The output mixer, as shown, comprises a tube 14 illustrated as a triode whose plate is connected through a resistor l5 to the line 58 and through a blocking condenser it to the swell control 'resistor 30. The control grid of the tube 1 is connected through a wiper T? to a resistor 73 in series in the line 26. By adjusting the wiper l1, an over-all volume adjustment can be made as, for example, to limit the volume, it being understood that the output volume is subject to further overall variation :by adjustment of the swell control wiper-29.

Figure 3 illustrates a typical circuit which can be used for the several stop mixers including a tube 8| whose plate is connected through a resistor 82 to a suitable source of plate potential and through a blocking condenser 83 and resistor 84 to the output line 26. The control grid of the tube is supplied with flute type vibrations through a resistor 85 and with string type vibrations through a similar resistor 86. A control switch device, each of the mixing devices including an electron discharge tube having a control grid, a cathode and a plate, the sources being connected to the control grid and the translating device being connected to the plate, filter means in circuit with the control grid and the cathode, and a switch for starting and stopping operation of the tube.

2. An electrical musical instrument compris- 37 is provided across e grid Cathode Circuit of 10 ing sources of audible frequency vibrations of difthe e to Control its Operation ferent tonal qualities, a translating device, and In order to control the harmonic content of a plurality f mixing devices connected in par... e mixer ou p a filter circuit is provided across allel between each of the sources and the transthe gr d 6 0 6 Circuit of the tubes and, as lating device, each of the mixing devices includshown, includes a condenser 83 in series with a ing an electron discharge tube having a control resistor 89 and a series connected reactor 9! and grid, a cathode and a plate, the sources being resistor 9 parallel to the condenser 88 and connected to the control grid and the translating sistor 89. A third parallel circuit includes a redevice being onnected to the plate, filter means s r 93 al t is ay be o itt d i certain in circuit with the control grid and the cathode, f e s ops. The connection to the ca is and a short circuit switch between the control through a resistor 80 having a condenser 80 in grid d th cathode, parallel eW 3. An electrical musical instrument comprising The Circuit, as Shown, p des a band pass a series of oscillators for producing oscillations filter circuit Which y be designed to pass a r corresponding to different notes of a musical atively W e band of frequenc A filter f t i scale, each of the oscillators producing two osciltype will serve to filter or attenuate certain ranges lations of the same fundamental frequency and of qu s o than Others 0 p ce e of difierent harmonic content, an input mixer desired tone colors and the values of the several having two sections for separately transmitting filter elements can be controlled to provide subthe several oscillations of similar harmonic constantially any desired harmonic content in the tent, a translating device, and a plurality of stop output. Therefore, by proper selection of the mixers in parallel connecting the input mixer to values of the several circuit elements, substanthe translating device, each of the stop mixers tially any desired tonal effect can be obtained. including means to control the relative intensities Typical, although by no means limiting, values of the fundamental and the several harmonic frefor the several circuit elements of Figure 3 for a quencies and control means to control its operright hand mixer for several typical stops may ation. be as follows: EARLE L. KENT.

480K 0 K Omit Omit .005 Omit 0 50K Omit Omit .05 250K Omit 50K Omit Omit Omit 480K Omit Omit 0 ICE Omit 480K 0 Omit 0 1011 .01 250K Omit Omit Omit 10H Omit Diapason 250K Omit Omit 50K Omit Omit Omit Vox Humane Omit 480K 0 Omit 10K 10H .002

While several embodiments of the invention 50 REFERENCES CITED have been shown and described in detail, it will be understood that these are illustrative only and are not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

1. An electrical musical instrument comprising sources of audible frequency vibrations of different tonal qualities, a translating device, and a plurality of mixing devices connected in parallel between each of the sources and the translating The following references are of record in the file of this patent:

UNITED STATES PATENTS 

